Flexible display device and manufacturing method thereof

ABSTRACT

A flexible display device includes: a first flexible substrate and a second flexible substrate facing each other; a display part positioned on a surface of the first flexible substrate facing the second flexible substrate and including a plurality of thin film transistors and a plurality of light emitting elements; a color filter positioned on a surface of the second flexible substrate facing the first flexible substrate; an overcoat layer positioned between the display part and the color filter and covering the color filter; a gas barrier layer positioned between the display part and the overcoat layer and covering the overcoat layer; and an encapsulation part including a filler positioned between the display part and the gas barrier layer, and a sealant positioned at an outside of the filler, and an area of the gas barrier layer is larger than an area of the encapsulation part.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2016-0177825, filed on Dec. 23, 2016 in the KoreanIntellectual Property Office, the entire content of which isincorporated herein by reference.

BACKGROUND 1. Field

Aspects of embodiments of the present disclosure relate to a flexibledisplay device.

2. Description of the Related Art

A typical organic light emitting diode display device includes asubstrate, a display part positioned on the substrate and including aplurality of thin film transistors and a plurality of organic lightemitting diodes, and an encapsulation part that seals the display partto block moisture and oxygen included in outside air from penetratingthereto.

In a case of a small-sized organic light emitting diode display device,the encapsulation part may be a thin film encapsulation in which aplurality of inorganic layers and a plurality of organic layers arealternately stacked one by one. In a middle-sized or large-sized organiclight emitting diode display device, the encapsulation part may includea sealing substrate made of a glass material and a sealant forintegrally bonding edges of a substrate and the sealing substrate.

In a case of a large-sized flexible organic light emitting diode displaydevice, it is difficult to realize flexibility of a sealing substratemade of a glass material, and it is disadvantageous to realize a displaydevice to be thin. The thin film encapsulation has excellentflexibility, but when it is applied to a long manufacturing process, ayield (proportion of output to input of goods) is low.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the describedtechnology and, therefore, it may contain information that does not formthe prior art that is already known in this country to a person ofordinary skill in the art.

SUMMARY

According to an aspect of embodiments of the present invention, a largeand thin flexible display device and a manufacturing method thereof mayimprove a sealing effect of a display part, without a sealing substratemade of a glass material, or a thin film encapsulation.

According to one or more exemplary embodiments, a flexible displaydevice includes: a first flexible substrate, a second flexiblesubstrate, a display part, a color filter, an overcoat layer, a gasbarrier layer, and an encapsulation part. The first flexible substrateand the second flexible substrate face each other. The display part ispositioned on a surface of the first flexible substrate facing thesecond flexible substrate, and includes a plurality of thin filmtransistors and a plurality of light emitting elements. The color filteris positioned on a surface of the second flexible substrate facing thefirst flexible substrate. The overcoat layer is positioned between thedisplay part and the color filter, and covers the color filter. The gasbarrier layer is positioned between the display part and the overcoatlayer, and covers the overcoat layer. The encapsulation part includes afiller positioned between the display part and the gas barrier layer,and a sealant positioned at an outside of the filler. An area of the gasbarrier layer is larger than an area of the encapsulation part.

An outer side of the sealant may be spaced apart from an outer edge ofthe gas barrier layer in a direction toward a center of the displaypart. The encapsulation part may further include a getter layerpositioned between the filler and the sealant.

An area of the gas barrier layer may be larger than that of the overcoatlayer. The gas barrier layer may be formed as a single layer made of oneof a silicon nitride, a silicon oxide, and a silicon oxynitride, or astacked layer thereof.

In a manufacturing method of a flexible display device according to oneor more exemplary embodiments, a buffer layer and a display part arearranged on a first flexible substrate. An encapsulation part includinga filler covering the display part and a sealant positioned at an outeredge of the filler is arranged on the display part. A second flexiblesubstrate is arranged on a carrier substrate. A color filter including aplurality of filter layers and a dark colored layer is arranged on thesecond flexible substrate. An overcoat layer and a gas barrier layer arearranged on the color filter. The first flexible substrate and thesecond flexible substrate are stacked such that the encapsulation partand the gas barrier layer contact each other, and then the sealant iscured. The carrier substrate is separated from the second flexiblesubstrate.

The first flexible substrate may include glass, and the second flexiblesubstrate may be a plastic film. A process temperature of the colorfilter and a process temperature of the gas barrier layer may be higherthan a process temperature of the display part. An area of the gasbarrier layer may be larger than an area of the overcoat layer and anarea of the encapsulation part, and an outer side of the sealant may bespaced apart from an outer edge of the gas barrier layer in a directiontoward a center of the display part.

In a manufacturing method of a flexible display device according to oneor more exemplary embodiments, a first flexible substrate is arranged ona carrier substrate. A buffer layer and a display part are arranged onthe first flexible substrate. An encapsulation part including a fillercovering the display part, and a sealant positioned at an outside of thefiller is arranged on the display part. A second flexible substrate isarranged on another carrier substrate. A color filter including aplurality of filter layers and a dark colored layer is arranged on thesecond flexible substrate. An overcoat layer and a gas barrier layer arearranged on the color filter. The first flexible substrate and thesecond flexible substrate are stacked such that the encapsulation partand the gas barrier layer contact each other, and then the sealant iscured. The carrier substrate is separated from the first flexiblesubstrate, and the another carrier substrate is separated from thesecond flexible substrate.

The first flexible substrate and the second flexible substrate may beplastic films. A process temperature of the color filter and a processtemperature of the gas barrier layer may be higher than a processtemperature of the display part. An area of the gas barrier layer may belarger than an area of the overcoat layer and an area of theencapsulation part, and an outer side of the sealant may be spaced apartfrom an outer edge of the gas barrier layer in a direction toward acenter of the display part.

According to an aspect of the flexible display device according to oneor more exemplary embodiments, it is possible to ensure sealingperformance of a display part, to have a large size and a thinthickness, and increase a manufacturing yield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 to FIG. 4 illustrate cross-sectional views of a manufacturingprocess of a flexible display device, according to an exemplaryembodiment.

FIG. 5 illustrates a cross-sectional view of a flexible display deviceaccording to an exemplary embodiment.

FIG. 6 to FIG. 9 illustrate cross-sectional views of a manufacturingprocess of a flexible display device, according to another exemplaryembodiment.

FIG. 10 illustrates a cross-sectional view of a flexible display deviceaccording to an exemplary embodiment.

FIG. 11 illustrates a partial enlarged cross-sectional viewcorresponding to the cross-sectional view of FIG. 5.

DETAILED DESCRIPTION

The present disclosure will be described more fully herein withreference to the accompanying drawings, in which some exemplaryembodiments of the disclosure are shown. As those skilled in the artwould realize, the described embodiments may be modified in variousdifferent ways, all without departing from the spirit or scope of thepresent disclosure.

To more clearly describe the present disclosure, portions which do notrelate to the description may be omitted, and like reference numeralsdesignate like elements throughout the specification.

Further, the size and thickness of each component shown in the drawingsmay be arbitrarily shown for better understanding and ease ofdescription, but the present disclosure is not limited thereto. In thedrawings, the thicknesses of layers, films, panels, regions, areas,etc., may be exaggerated for clarity.

It is to be understood that when an element, such as a layer, film,region, or substrate is referred to as being “on” another element, itmay be directly on the other element, or one or more interveningelements may also be present. In contrast, when an element is referredto as being “directly on” another element, there are no interveningelements present.

Further, in the specification, words such as “on” or “above” meanpositioned on or below the object portion, and do not necessarily meanpositioned on the upper side of the object portion based on agravitational direction.

In addition, unless explicitly described to the contrary, the word“comprise” and variations such as “comprises” or “comprising” are to beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements.

Herein, a manufacturing method of a flexible display device according toan exemplary embodiment will be described with reference to FIG. 1 toFIG. 4. FIG. 1 to FIG. 4 illustrate cross-sectional views of amanufacturing process of a flexible display device, according to anexemplary embodiment.

Referring to FIG. 1, a buffer layer 110 and a display part 200 aresequentially formed on a first flexible substrate 100, and anencapsulation part 300 is formed on the display part 200.

The first flexible substrate 100 may be made of thin glass that may bebent by an external force. The thin glass has a higher shape maintainingforce than a plastic film that may be used as a flexible substrate, and,thus, it may maintain flatness and be easily handled in a manufacturingprocess without an additional carrier substrate.

The buffer layer 110 prevents or substantially prevents impurities frompenetrating into the display part 200 and flattens a surface on whichthe display part 200 is positioned. The buffer layer 110 may be formedas a single layer made of one of a silicon nitride (SiNx), a siliconoxide (SiOx), and a silicon oxynitride (SiON), or a stacked layerthereof.

The buffer layer 110 may entirely cover a surface of the first flexiblesubstrate 100, and the display part 200 has a smaller area than thefirst flexible substrate 100 in consideration of disposition of wires,control elements, and a sealant 320 described further later herein.

The display part 200 is formed on the buffer layer 110. The display part200 includes a plurality of thin film transistors, a plurality ofcapacitors, and a plurality of light emitting elements. The display part200 includes a plurality of pixels PX, and each pixel PX may include aplurality of subpixels, such as, a red subpixel SP1, a green subpixelSP2, and a blue subpixel SP3, for example. In an embodiment, at leasttwo thin film transistors, at least one capacitor, and one lightemitting element are positioned for each of the subpixels SP1, SP2, andSP3.

In an embodiment, the buffer layer 110 may be formed by a hightemperature chemical vapor deposition (CVD) process at 100° C. or more,and the display part 200 may be formed by a low temperature chemicalvapor deposition (CVD) process at 100° C. or less. A further detailedstructure of the display part 200 will be described later herein.

The encapsulation part 300 is formed on the display part 200. Theencapsulation part 300 includes a filler 310 covering the display part200, and a sealant 320 positioned on the buffer layer 110 at an outside,or along an edge, of the filler 310. The encapsulation part 300 mayinclude a getter layer 330 positioned between the filler 310 and thesealant 320.

The filler 310 absorbs external impact, and allows the first flexiblesubstrate 100 and a second flexible substrate described later herein tobe spaced apart from each other by a distance (e.g., a predetermineddistance). The filler 310 may include a material with hightransmittance, such as, one of an epoxy, polyimide, urethane acrylate,epoxy acrylate, and silicone-based resin, for example.

In an embodiment, the sealant 320 may include an ultraviolet ray curingresin. The getter layer 330 absorbs oxygen and moisture to preventdeterioration of the display part 200 due to the oxygen and themoisture. The getter layer 330 may include a mixture of a metal oxide,such as calcium oxide (CaO) and selenium oxide (SeO), in a powder form,and an acrylic resin. The filler 310 has an area that is larger thanthat of the display part 200 and smaller than that of the buffer layer110, and the sealant 320 and the getter layer 330 are positioned on thebuffer layer 110 at an outer side of the filler 310.

Referring to FIG. 2, a first carrier substrate 410 is prepared, and thena first sacrificial layer 411 is formed on the first carrier substrate410. A second flexible substrate 500 is formed on the first sacrificiallayer 411 or a previously manufactured second flexible substrate 500 isdisposed thereon, and a color filter 600, an overcoat layer 510, and agas barrier layer 520 are sequentially formed on the second flexiblesubstrate 500.

The first carrier substrate 410 is made of a rigid material, such asglass or a metal, and the first sacrificial layer 411 may includeamorphous silicon, a metal, an organic material, or the like.

In the manufacturing process of the flexible display device, the firstcarrier substrate 410 supports the second flexible substrate 500,maintains flatness thereof, and allows it to be easily handled. In afinal manufacturing process, the first carrier substrate 410 isseparated from the second flexible substrate 500.

When the second flexible substrate 500 is formed on the firstsacrificial layer 411, the second flexible substrate 500 may be formedin a method in which a transparent resin is coated on the firstsacrificial layer 411 and then cured. In an embodiment, the secondflexible substrate 500 may include one of polyethylene terephthalate,polyethylene naphthalate, and polyimide.

The color filter 600 is formed on the second flexible substrate 500. Thecolor filter 600 includes a plurality of filter layers 610 and darkcolored layers 620 positioned between the plurality of filter layers610. In an embodiment, the plurality of filter layers 610 may include ared filter layer 610R corresponding to the red subpixel SP1, a greenfilter layer 610G corresponding to the green subpixel SP2, and a bluefilter layer 6106 corresponding to the blue subpixel SP3.

The filter layers 610 absorb light of remaining wavelengths except forwavelengths corresponding to their respective colors among incidentexternal light (of visible light wavelengths). In addition, the darkcolored layer 620 absorbs most of incident external light. Accordingly,when light emitted from any of the subpixels SP1, SP2, and SP3 ofpredetermined colors passes through the respective filter layer 610 andis emitted to the outside, since the light does not mix with externallight of another wavelength, the color filter 600 suppresses reflectionof the external light and increases color purity.

In an embodiment, the plurality of filter layers 610 may include anacrylic resin or a polyimide-based resin, and the dark colored layers620 may include one of chromium (Cr), chromium oxide (CrOx), chromiumnitride (CrNx), carbon black, a pigment mixture, and a dye mixture.

In an embodiment, a process temperature of the color filter 600 is equalto or greater than 100° C., and is higher than that of the display part200. If the color filter 600 were directly formed on the encapsulationpart 300, the display part 200 may be damaged due to the processtemperature of the color filter 600. Therefore, instead of being formedon the encapsulation part 300, the color filter 600 is formed on thesecond flexible substrate 500, thereby preventing damage to the displaypart 200.

The overcoat layer 510 is formed on the color filter 600. The overcoatlayer 510 protects the color filter 600, improving reliability of thecolor filter 600. In an embodiment, the overcoat layer 510 may includean acrylic resin or a polyimide-based resin. An area of the overcoatlayer 510 may be larger than that of the color filter 600 and smallerthan that of the second flexible substrate 500.

The gas barrier layer 520 is formed on the overcoat layer 510. The gasbarrier layer 520 blocks diffusion of out-gas emitted from the colorfilter 600, thereby suppressing deterioration of the display part 200.The gas barrier layer 520 may have a larger area than the overcoat layer510, and may have the same area as the second flexible substrate 500.

In an embodiment, the gas barrier layer 520 may be formed as a singlelayer made of one of a silicon nitride (SiNx), a silicon oxide (SiOx),and a silicon oxynitride (SiON), or a stacked layer thereof. In anembodiment, the gas barrier layer 520 may be formed by a hightemperature chemical vapor deposition (CVD) process at 100° C. or more.However, the process temperature of the gas barrier layer 520 is lowerthan a decomposition start temperature (i.e. about 230° C.) of the colorfilter 600 and the overcoat layer 510 such that the color filter 600 andthe overcoat layer 510 may be separated from each other at the processtemperature of the gas barrier layer 520.

Referring to FIG. 3, the first flexible substrate 100 and the secondflexible substrate 500 are overlapped with each other such that theencapsulation part 300 and the gas barrier layer 520 contact each other.In FIG. 3, it is illustrated that the second flexible substrate 500 ispositioned on the first flexible substrate 100, but, conversely, it isalso possible for the first flexible substrate 100 to be positioned onthe second flexible substrate 500.

The first flexible substrate 100 and the second flexible substrate 500are integrally bonded by the curing of the sealant 320. In anembodiment, the sealant 320 includes an ultraviolet ray curing resin,and an ultraviolet ray irradiating device (not shown) is used toirradiate ultraviolet rays to the sealant 320.

Referring to FIG. 4, the first carrier substrate 410 is separated fromthe second flexible substrate 500. In an embodiment, for example, thefirst sacrificial layer 411 includes amorphous silicon, and it ispossible to separate the first carrier substrate 410 and the secondflexible substrate 500 by irradiating a laser beam to the firstsacrificial layer 411 to eliminate the first sacrificial layer 411. Inthis case, any of various types of lasers, such as an excimer laser, asolid state laser, and a pulse laser, may be used.

After the first carrier substrate 410 is separated, a passivation film(not shown) may be attached to an outer surface of the second flexiblesubstrate 500. The passivation film protects the second flexiblesubstrate 500 from external impact and scratches.

A flexible display device according to an exemplary embodiment will bedescribed with reference to FIG. 5. FIG. 5 illustrates a cross-sectionalview of a flexible display device according to an exemplary embodiment,such as manufactured by the manufacturing method of the flexible displaydevice according to the exemplary embodiment shown in FIG. 1 to FIG. 4.Further detailed descriptions for the respective constituent elementsdescribed with reference to FIG. 1 to FIG. 4 will be omitted.

Referring to FIG. 5, an area of the gas barrier layer 520 is larger thanthat of the encapsulation part 300 including the filler 310, the sealant320, and the getter layer 330. A surface of the sealant 320 arrangedtoward the second flexible substrate 500 contacts a surface of the gasbarrier layer 520, and an outer side surface of the sealant 320 isspaced apart from an edge of the gas barrier layer 520 at a distance(e.g., a predetermined distance) toward the display part 200.

Accordingly, the gas barrier layer 520, the sealant 320, the getterlayer 330, and the filler 310 are sequentially positioned along asurface direction or lateral direction (e.g., a horizontal directionwith respect to the drawing) of the first flexible substrate 100 or thesecond flexible substrate 500 from an outer side of the flexible displaydevice. That is, the gas barrier layer 520 may extend further toward theouter side of the flexible display device than the sealant 320, thegetter layer 330, and the filler 310.

The gas barrier layer 520 blocks out-gas of the color filter 600 fromdiffusing into the display part 200, and also blocks moisture and oxygencontained in outside air from diffusing or penetrating toward thedisplay unit 200. The gas barrier layer 520 and the encapsulation part300 seal the display part 200, preventing or substantially preventingthe moisture and oxygen contained in the outside air from penetratinginto the display part 200.

The flexible display device of the above-described exemplary embodimentuses an excellent flexible and thin plastic film as the sealingsubstrate (i.e. the second flexible substrate 500), and includes theencapsulation part 300 including the filler 310, the sealant 320, andthe getter layer 330 instead of a thin film encapsulation having a lowyield in a long manufacturing process. Accordingly, the flexible displaydevice according to an exemplary embodiment may be large and thin, and ahigh manufacturing yield may be obtained.

A manufacturing method of a flexible display device according to anotherexemplary embodiment will be described with reference to FIG. 6 to FIG.9. FIG. 6 to FIG. 9 illustrate cross-sectional views of a manufacturingprocess of a flexible display device, according to another exemplaryembodiment.

Referring to FIG. 6, a second carrier substrate 420 is prepared, andthen a second sacrificial layer 421 is formed on the second carriersubstrate 420. A first flexible substrate 100′ is formed on the secondsacrificial layer 421, or a previously manufactured first flexiblesubstrate 100′ is disposed thereon. The buffer layer 110 and the displaypart 200 are sequentially formed on the first flexible substrate 100′,and the encapsulation part 300 is formed on the display part 200.

In an embodiment, the second carrier substrate 420 is made of a rigidmaterial such as glass or a metal, and the second sacrificial layer 421may include amorphous silicon, a metal, an organic material, or thelike.

When the first flexible substrate 100′ is formed on the secondsacrificial layer 421, the first flexible substrate 100′ may be formedin a method in which a transparent resin is coated on the secondsacrificial layer 421 and then cured. In an embodiment, the firstflexible substrate 100′ may include one of polyethylene terephthalate,polyethylene naphthalate, and polyimide.

The buffer layer 110 and the display part 200 are sequentially formed onthe first flexible substrate 100′, and the encapsulation part 300 isformed on the display part 200. The buffer layer 110, the display part200, and the encapsulation part 300 may be the same as in theabove-described exemplary embodiment, and a duplicate descriptionthereof will be omitted.

Referring to FIG. 7, a third carrier substrate 430 is prepared, and thena third sacrificial layer 431 is formed on the third carrier substrate430. The second flexible substrate 500 is formed on the thirdsacrificial layer 431, or a previously manufactured second flexiblesubstrate 500 is disposed thereon. The color filter 600, the overcoatlayer 510, and the gas barrier layer 520 are sequentially formed on thesecond flexible substrate 500.

The third carrier substrate 430 and the third sacrificial layer 431 maybe the same as the first carrier substrate 410 and the first sacrificiallayer 411 of the above-described exemplary embodiment, and the colorfilter 600, the overcoat layer 510, and the gas barrier layer 520 may bethe same as those of the above-described exemplary embodiment, and aduplicate description thereof will be omitted.

Referring to FIG. 8, the first flexible substrate 100 and the secondflexible substrate 500 are overlapped with each other such that theencapsulation part 300 and the gas barrier layer 520 contact each other,and the first flexible substrate 100′ and the second flexible substrate500 are integrally bonded by curing of the sealant 320.

Referring to FIG. 9, the second carrier substrate 420 is separated fromthe first flexible substrate 100′, and the third carrier substrate 430is separated from the second flexible substrate 500. In an embodiment,for example, the second sacrificial layer 421 and the third sacrificiallayer 431 include amorphous silicon, and it is possible to separate thesecond carrier substrate 420 and the third carrier substrate 430 byirradiating a laser beam to the second sacrificial layer 421 and thethird sacrificial layer 431 to eliminate the second sacrificial layer421 and the third sacrificial layer 431.

After the second carrier substrate 420 and the third carrier substrate430 are separated, passivation films (not shown) may be attached toouter surfaces of the first flexible substrate 100′ and the secondflexible substrate 500. The passivation films protect the first flexiblesubstrate 100′ and the second flexible substrate 500 from externalimpact and scratches.

A flexible display device according to an exemplary embodiment will bedescribed with reference to FIG. 10. FIG. 10 illustrates across-sectional view of the flexible display device according to anexemplary embodiment, such as manufactured by the method described abovewith reference to FIG. 6 to FIG. 9.

Referring to FIG. 10, the area of the gas barrier layer 520 is largerthan that of the encapsulation part 300 including the filler 310, thesealant 320, and the getter layer 330. A surface of the sealant 320arranged toward the second flexible substrate 500 contacts a surface ofthe gas barrier layer 520, and an outer side surface of the sealant 320is spaced apart from an edge of the gas barrier layer 520 at a distance(e.g., a predetermined distance) toward the display part 200.

Accordingly, the gas barrier layer 520, the sealant 320, the getterlayer 330, and the filler 310 are sequentially positioned along asurface direction or lateral direction (e.g., a horizontal directionwith respect to the drawing) of the first flexible substrate 100′ or thesecond flexible substrate 500 from an outer side of the flexible displaydevice toward an inner side thereof. The gas barrier layer 520 and theencapsulation part 300 protect the display part 200, preventing orsubstantially preventing the moisture and oxygen contained in theoutside air from penetrating into the display part 200.

The flexible display device according to an exemplary embodiment usesexcellent flexible and thin plastic films as the first flexiblesubstrate 100′ and the second flexible substrate 500, and includes theencapsulation part 300 including the filler 310, the sealant 320, andthe getter layer 330 instead of a thin film encapsulation having a lowyield in a long manufacturing process. Accordingly, the flexible displaydevice of the exemplary embodiment may be large and thin, and a highmanufacturing yield may be obtained.

FIG. 11 illustrates a partial enlarged cross-sectional viewcorresponding to the cross-sectional view of FIG. 5. A further detailedstructure of the display part will be described with reference to FIG.11.

Referring to FIG. 11, the buffer layer 110 and the display part 200 arepositioned on the first flexible substrate 100. In an embodiment, thefirst flexible substrate 100 may be made of thin glass or a plasticfilm, and the buffer layer 110 may be formed as a single layer made ofone of a silicon nitride (SiNx), a silicon oxide (SiOx), and a siliconoxynitride (SiON), or a stacked layer thereof.

The display part 200 includes the plurality of pixels PX, and the pixelPX includes the plurality of subpixels. For example, one pixel PX mayinclude the red subpixel SP1, the green subpixel SP2, and the bluesubpixel SP3. In an embodiment, at least two thin film transistors 800,at least one capacitor 900, and one light emitting element 700R, 700G,or 700B are positioned for each of the sub-pixels SP1, SP2, and SP3.

A semiconductor layer 810 is positioned on the buffer layer 110. Thesemiconductor layer 810 may include a polysilicon or oxidesemiconductor, and the semiconductor layer 810 including the oxidesemiconductor may be covered by an additional passivation layer. Thesemiconductor layer 810 includes a channel region that is not doped withimpurities, and a source region and a drain region that are doped withimpurities.

A gate insulating layer 120 may be positioned on the semiconductor layer810. The gate insulating layer 120 may be formed as a single layer madeof a silicon nitride (SiNx) or a silicon oxide (SiOx), or a stackedlayer thereof. A gate electrode 820 and a first capacitor plate 910 maybe positioned on the gate insulating layer 120. The gate electrode 820overlaps the channel region of the semiconductor layer 810.

An interlayer insulating layer 130 may be positioned on the gateelectrode 820 and the first capacitor plate 910. The interlayerinsulating layer 130 may be formed as a single layer made of a siliconnitride (SiNx) or a silicon oxide (SiOx), or a stacked layer thereof. Asource electrode 830, a drain electrode 840, and a second capacitorplate 920 may be positioned on the interlayer insulating layer 130.

The source electrode 830 and the drain electrode 840 are respectivelyconnected to the source region and the drain region of the semiconductorlayer 810 by a via-hole passing through the interlayer insulating layer130 and the gate insulating layer 120. The source electrode 830 and thedrain electrode 840 may be formed as a multi-layered metal layer, suchas molybdenum (Mo)/aluminum (Al)/molybdenum (Mo) or titanium(Ti)/aluminum (AD/titanium (Ti).

The second capacitor plate 920 overlaps the first capacitor plate 910,and the first capacitor plate 910 and the second capacitor plate 920form the capacitor 900 using the interlayer insulating layer 130 as adielectric material. Alternatively, unlike the above-describedconfiguration, the first capacitor plate 910 may be positioned at thesame layer as the semiconductor layer 810, and the second capacitorplate 920 may be positioned at the same layer as the gate electrode 820.In FIG. 11, a top gate type of thin film transistor 800 is shown as anexample, but the thin film transistor 800 is not limited to the shownstructure.

A planarization layer 140 may be positioned on the thin film transistor800 and the capacitor 900. The planarization layer 140 may be formed asa single layer made of an inorganic or organic insulation material, or astacked layer thereof.

A pixel electrode 710 may be positioned on the planarization layer 140.The pixel electrode 710 is disposed at each of the subpixels SP1, SP2,and SP3, and is connected to the drain electrode 840 of the thin filmtransistor 800 through a via-hole passing through the planarizationlayer 140. A pixel defining layer (or partition wall) 150 may bepositioned on the planarization layer 140 and on an edge of the pixelelectrode 710.

Emission layers 720R, 720G, and 720B may be positioned on the pixelelectrode 710, and a common electrode 730 may be positioned on theemission layers 720R, 720G, and 720B and the pixel defining layer 150.In an embodiment, the common electrode 730 may be positioned on theentire display area. One of the pixel electrode 710 and the commonelectrode 730 functions as an anode for injecting holes into theemission layers 720R, 720G, and 720B, and the other thereof functions asa cathode for injecting electrons into the emission layers 720R, 720G,and 720B.

The emission layers 720R, 720G, and 720B may be divided into a redemission layer 720R positioned at the red subpixel SP1, a green emissionlayer 720G positioned at the green subpixel SP2, and a blue emissionlayer 720B positioned at the blue subpixel SP3. The emission layers720R, 720G, and 720B may include an organic emission layer, and mayfurther include at least one of a hole injection layer, a holetransporting layer, an electron transporting layer, and an electroninjection layer.

The hole injection layer and the hole transporting layer are positionedbetween the anode and the organic emission layer, and the electrontransporting layer and the electron injection layer are positionedbetween the cathode and the organic emission layer. The electron andhole are coupled with each other in the emission layers 720R, 720G, and720B to generate an exciton, and light is emitted by energy generatedwhen the exciton falls from an excited state to a ground state.

In an embodiment, the pixel electrode 710 may be formed as a reflectivelayer, and the common electrode 730 may be formed as a transparent layeror a semi-transparent layer. Thereby, light emitted from the emissionlayers 720R, 720G, and 720B is reflected by the pixel electrode 710, andpasses through the common electrode 730 and the color filter 600 to beemitted to the outside.

The color filter 600 may include the red filter layer 610R correspondingto the red subpixel SP1, the green filter layer 610G corresponding tothe green subpixel SP2, and the blue filter layer 6106 corresponding tothe blue subpixel SP3. The color filter 600 may include the dark coloredlayer 620 positioned between the plurality of filter layers 610.

The filter layers 610 absorb light of the remaining wavelength exceptfor wavelengths corresponding to their respective colors among externallight incident on the flexible display device, and the dark coloredlayer 620 absorbs most of the external light. Accordingly, light emittedfrom any of the emission layers 720R, 720G, and 720B of predeterminedcolors does not mix with external light of the other wavelengths, and,thus, the flexible display device may suppress reflection of theexternal light through the color filter 600 and increase color purity.

The color filter 600 is covered with the overcoat layer 510 and the gasbarrier layer 520. The overcoat layer 510 protects the color filter 600,improving reliability of the color filter 600, and the gas barrier layer520 blocks diffusion of out-gas of the color filter 600 toward thedisplay part 200, suppressing degradation of the display part 200.

The display part 200 is primarily sealed by the encapsulation part 300provided with the filler 310, the sealant 320, and the getter layer 330,and is secondarily sealed by the gas barrier layer 520 having a largerarea than the encapsulation part 300. That is, the gas barrier layer 520performs an additional sealing function to block moisture and oxygen ofoutside air penetrating from the outside of the encapsulation part 300.

While this disclosure has been described in connection with what arepresently considered to be some practical exemplary embodiments, it isto be understood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A flexible display device comprising: a firstflexible substrate and a second flexible substrate facing each other; adisplay part positioned on a surface of the first flexible substratefacing the second flexible substrate and including a plurality of thinfilm transistors and a plurality of light emitting elements; a colorfilter positioned on a surface of the second flexible substrate facingthe first flexible substrate; an overcoat layer positioned between thedisplay part and the color filter and covering the color filter; a gasbarrier layer positioned between the display part and the overcoat layerand covering the overcoat layer; and an encapsulation part including afiller positioned between the display part and the gas barrier layer,and a sealant positioned at an outside of the filler, wherein the gasbarrier layer extends between the sealant and the surface of the secondflexible substrate and contacts a peripheral side of the overcoat layerthat extends in a direction from the second flexible substrate towardthe first flexible substrate, and an area of the gas barrier layer islarger than each of an area of the encapsulation part and an area of theovercoat layer.
 2. The flexible display device of claim 1, wherein anouter side of the sealant is spaced apart from an outer edge of the gasbarrier layer in a direction toward a center of the display part.
 3. Theflexible display device of claim 2, wherein the encapsulation partfurther includes a getter layer positioned between the filler and thesealant.
 4. The flexible display device of claim 1, wherein the gasbarrier layer is formed as a single layer made of one of a siliconnitride, a silicon oxide, and a silicon oxynitride, or a stacked layerthereof.
 5. The flexible display device of claim 1, wherein the firstflexible substrate comprises glass, and the second flexible substratecomprises a plastic film.
 6. The flexible display device of claim 1,wherein each of the first flexible substrate and the second flexiblesubstrate comprises a plastic film.